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La maladie d’Alzheimer (MA) est une affection neurodégénérative qui se caractérise par un début insidieux, un déclin progressif des fonctions cognitives, l’apparition inconstante mais fréquente de perturbations non cognitives (troubles psychologiques et comportementaux) et qui entraîne inexorablement une perte d’autonomie fonctionnelle. La MA démentielle correspond à la phase de la maladie au cours de laquelle les symptômes cliniques (touchant la mémoire et d’autres domaines) sont suffisants pour altérer les activités de la vie quotidienne. La MA typique (forme commune) est caractérisée par l’installation d’un déficit progressif précoce et significatif de la mémoire épisodique qui restera toujours dominant dans l’évolution au cours de laquelle il s’associera à d’autres troubles cognitifs (dysexécutifs, apraxiques, aphasiques ou agnosiques visuels), et psychiatriques, par la présence de biomarqueurs.

How to diagnose an Alzheimer’s disease ?Alzheimer’s disease (AD) is the most common progressive neurodegenerative disease and the most common form of dementia in the elderly. It is a complex disorder with environmental and genetic components. There are two major types of AD, early onset and the more common late onset. In progression to Alzheimer’s disease, generally low cognitive function and general atrophy are involved, Careful cognitive assessment may aid differential diagnosis between different types of dementia and can provide theoretical insight into the nature of the underlying impairments. Behavioral and psychological symptoms of dementia represent common clinical features of dementias, contributing to the heterogeneous phenotypic expression of Alzheimer’s disease. Recently proposed diagnostic criteria, in addition to the clinical neuropsychological examination aimed at identifying the typical AD symptoms, include staging criteria based on AD biological measures related to its pathology. Despite the obvious benefits of these new criteria, an accurate diagnosis is not always easily reached because, particularly in its earliest stages, the symptoms of the disease are very variable. Biological measures, or biomarkers, of the disease should first facilitate an early and accurate diagnosis, have a prognostic and predictive value, and have the capacity to monitor therapeutic efficacy Amyloid imaging and CSF tau/A β ratio may be useful in the differential diagnosis with other neurodegenerative dementias, especially, in early onset cases.